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btree.c
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btree.c
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//
// Created by @hbFree on 1/3/2020.
//
#include "btree.h"
pile *pile_init() {
pile *p = (pile *) malloc(sizeof(pile));
p->head = NULL;
return p;
}
// insert at beginning
void push(pile *p, pile_dtype val) {
pnode *node = (pnode *) malloc(sizeof(pnode));
node->val = val;
node->next = p->head;
p->head = node;
}
// gotta check if empty before
pile_dtype pop(pile *p) {
if (p->head) // check not empty
{
pile_dtype ret = p->head->val;
pnode *tmp = p->head;
p->head = p->head->next;
free(tmp);
return ret;
}
}
int empty(pile *p) {
if (!p->head)
return 1; // empty
return 0;
}
void pile_destroy(pile *p) {
pnode *node = p->head;
while (node) {
pnode *nxt = node->next;
free(node);
node = nxt;
}
p->head = NULL; // just in case used even after freed
free(p);
}
// return @ of an empty new created node
btree_node *btree_new_node() {
btree_node *ret = (btree_node *) malloc(sizeof(btree_node));
ret->n_elts = 0; // no data yet
for (int i = 0; i < BTREE_DATA_MAX + 1; ++i) // no kids too
ret->kids[i] = NULL;
return ret;
}
// new btree with NULL root
// init with comparator
btree btree_init(int (*comparator)(btree_dtype, btree_dtype)) {
btree ret;
ret.root = NULL;
ret.comparator = comparator;
return ret;
}
// destroy the tree
void btree_destroy(btree bt) {
if (bt.root == NULL)
return;
// destroy kids if got any (recursive)
for (int i = 0; i < bt.root->n_elts + 1; i++) // +1 since nKids = nElts + 1
if (bt.root->kids[i] != NULL) {
btree kid_tree = {bt.root->kids[i], NULL};
btree_destroy(kid_tree);
}
free(bt.root);
}
int ArrayBSearch(bs_dtype *arr, int n_elts, bs_dtype val, int *found, int (*cmp_fnc)(bs_dtype, bs_dtype)) {
int inf = 0, sup = n_elts - 1;
*found = 0; // not found by default
while (inf <= sup) {
int med = (inf + sup) / 2; // BSearch classic
int cmp = cmp_fnc(val, arr[med]);
if (cmp == 0) {
*found = 1;
return med;
}
if (cmp > 0) // val > middle value
inf = med + 1;
else
sup = med - 1;
}
return inf; // the place it should be
}
// return found, node & offset
// if not found then node & offset are where the value should be stored at
btree_seek_coord btree_seek(btree bt, btree_dtype val, int _addPile, pile *p) {
btree_seek_coord ret = {.node = NULL, .pos = -1};
if (bt.root == NULL || bt.comparator == NULL)
return ret; // invalid (shall be provided with valid node and comparator)
int found = -1;
ret.node = bt.root; // update last accessed node
int shd_be_placed = ArrayBSearch(bt.root->data, bt.root->n_elts, val, &found, bt.comparator);
if (found > 0) // found = true
{
ret.node = bt.root;
ret.pos = shd_be_placed;
return ret;
}
// if doesn't have a kid there
if (bt.root->kids[shd_be_placed] == NULL)
return ret;
// if has then seek at
btree kid_btree = {.root = bt.root->kids[shd_be_placed], .comparator = bt.comparator};
if (_addPile > 0)
push(p, bt.root);
return btree_seek(kid_btree, val, _addPile, p);
}
// insert val to the b-tree bt
// return 1 if success
// 0 if an error occurs
// -1 if value already in tree
int btree_insert(btree *bt, btree_dtype val) {
if (bt->comparator == NULL)
return 0; // btree not initiated
if (bt->root == NULL) {
bt->root = btree_new_node();
bt->root->data[0] = val;
bt->root->n_elts = 1;
return 1; // success
}
pile *p = pile_init(); // will contains the ascendants of the node which it should be in
btree_seek_coord sk = btree_seek(*bt, val, 1, p); // first of all search if it exists
if (sk.pos >= 0) // found ?
return -1; // value already inserted
btree_node *right = NULL;
while (sk.node != NULL) {
if (sk.node->n_elts < BTREE_DATA_MAX) // last accessed node has room for ?
{
int i = sk.node->n_elts - 1;
for (; i >= 0; --i) {
// move elements right till right place found
if (bt->comparator(sk.node->data[i], val) < 0)
break;
sk.node->data[i + 1] = sk.node->data[i]; // move right
sk.node->kids[i + 2] = sk.node->kids[i + 1]; // move kids
}
sk.node->data[i + 1] = val; // place node
sk.node->kids[i + 2] = right; // place right node
int j = 0;
sk.node->n_elts++;
return 1; // success
}
// if there's no room for then...
// alloc holder array
int array_len = 1 + sk.node->n_elts;
btree_dtype *seq = (btree_dtype *) malloc(sizeof(btree_dtype) * array_len);
int inserted = 0; // val isn't yet inserted in the array
int rkid_on_extreme = 0; // if the right kid shoud be inserted on the extreme right (can't no spance)
for (int i = 0; i < array_len - 1;) {
btree_dtype tmp = sk.node->data[i];
if (inserted > 0 || bt->comparator(val, tmp) > 0) // if inserted or val > tmp
{
seq[i + inserted] = tmp;
++i;
}
else
{
seq[i] = val;
sk.node->kids[i + 1] = right; // insert right node
inserted = 1;
}
}
if (!inserted) {
seq[sk.node->n_elts] = val; // if not inserted then it shall be on the extreme right
// sk.node->kids[sk.node->n_elts] = right; // if not inserted then it shall be on the extreme right
rkid_on_extreme = 1;
}
// now split into two nodes
int nElts = sk.node->n_elts;
int middle_index = (nElts + 1) / 2;
btree_dtype middle_val = sk.node->data[middle_index];
// store left half into original node (left node)
sk.node->n_elts = middle_index;
memmove(sk.node->data, seq, middle_index);
// create the right node
btree_node *right_node = btree_new_node();
memmove(right_node->data, seq + middle_index + 1, sizeof(btree_dtype) * (nElts - middle_index)); // copy data
memmove(right_node->kids, sk.node->kids + middle_index + 1,sizeof(btree_dtype) * (nElts - middle_index)); // copy kids
if(rkid_on_extreme)
right_node->kids[nElts - middle_index - 1] = right;
right_node->n_elts = nElts - middle_index;
memset(sk.node->kids + middle_index + 1, 0, nElts - middle_index); // nullify left node's rightest kids
// if has no parent
if (empty(p)) {
btree_node *parent = btree_new_node();
parent->n_elts = 1; // holds the middle value only
parent->data[0] = middle_val;
parent->kids[0] = sk.node; // left child
parent->kids[1] = right_node; // left child
bt->root = parent; // new root
return 1; // success
}
right = right_node;
val = middle_val; // new value to insert into parent
// if has parent
sk.node = pop(p);
free(seq);
}
pile_destroy(p);
return 1;
}
// return 1 if node is a leaf (doesn't have kids) - 0 if internal node
int is_leaf(btree_node *node)
{
if(!node)
return 0; // NULL isn't a node
int isLeaf = 1; // let's consider it an internal node (!leaf) and check if it is
for(int i = 0; i < node->n_elts + 1; ++i)
if(node->kids[i])
isLeaf = 0;
return isLeaf;
}
// gotta verify before if the two nodes at pos exist
void redistribute_kids_at(btree_node *node, int pos, int sense)
{
btree_node *left_node = node->kids[pos];
btree_node *right_node = node->kids[pos+1];
btree_dtype sep = node->data[pos]; // separator value
if(sense == REDISTRIBUTE_TO_RIGHT)
{
// redistribute left kid to its right brother
// move right
for(int i = right_node->n_elts; i >= 1 ; i--)
{
right_node->data[i] = right_node->data[i-1];
right_node->kids[i+1] = right_node->kids[i];
}
right_node->kids[1] = right_node->kids[0]; // first node gotta be moved right too
right_node->data[0] = sep;
right_node->kids[0] = left_node->kids[left_node->n_elts];
left_node->kids[left_node->n_elts] = NULL; // just in case some condition is made through
node->data[pos] = left_node->data[left_node->n_elts - 1];
right_node->n_elts++;
left_node->n_elts--;
}
else // REDISTRIBUTE_TO_LEFT
{
// redistribute right kid to its left brother
left_node->data[left_node->n_elts] = sep; // sep inserted as left's last value
node->data[pos] = right_node->data[0]; // first el replaces sep
left_node->kids[left_node->n_elts + 1] = right_node->kids[0];
right_node->n_elts--; // update total
// move left by 1 pos right_node's data & kids
for(int i = 0; i < right_node->n_elts; i++)
{
right_node->data[i] = right_node->data[i+1];
right_node->kids[i] = right_node->kids[i+1];
}
// last kid gotta be updated
right_node->kids[right_node->n_elts] = right_node->kids[right_node->n_elts+1];
right_node->kids[right_node->n_elts+1] = NULL; // just in case some condition was nmade through Nullity of a kid
left_node->n_elts++; // update total
}
}
int btree_delete(btree *bt, btree_dtype val)
{
}